PCC桩低应变反射波法检测时速度波形成机制探讨  

Formation mechanism of velocity waves in low strain integrity testing of PCC pile

作　　者：丁选明[1,2] 陈育民[1,3] 孔纲强[1,3] 

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,南京210098 [2]河海大学水资源高效利用与工程安全国家工程研究中心,南京210098 [3]河海大学岩土工程科学研究所,南京210098

出　　处：《岩土力学》2012年第1期154-161,共8页Rock and Soil Mechanics

基　　金：国家自然科学基金资助项目(No.51008115);江苏省自然科学基金创新学者攀登项目(No.BK2008040);河海大学中央高校基本科研业务费资助项目(No.2010B20514;No.2011B04514)

摘　　要：现浇混凝土大直径管桩(PCC桩)低应变检测时,桩头附近存在着明显的三维效应,表现在与激振点夹角不同的测点的速度响应存在着明显的差别。基于所建立的解析公式,研究了桩顶各振动模式的动力响应特征,分析了桩顶总体速度响应沿环向和径向的变化规律。研究结果表明:90o点的总体速度响应主要来源于轴对称模式,45o点、135o点和180o点的桩底反射峰大小和到达时间与轴对称模式接近,但入射波峰大小和到达时间与轴对称模式差别较大;桩顶速度响应主要来源于径向第1阶的模式,第2阶以上的模式贡献较小;各点速度响应主要是前几阶模式的叠加结果,环向第10阶以上的振动模式对总体速度响应的贡献较小;各模式对入射波峰的形成都有较大贡献,但反射波峰主要来自轴对称模式的贡献;高频干扰峰主要来自第1阶非轴对称模式,各点干扰波峰值、相位不一,90o点干扰波峰值最小,0o～90o点与90o～180o点相位相反;环向各点的速度响应差别较大,但沿径向的变化却不很明显。The three dimensional effect in low strain integrity testing of cast-in-place large-diameter pipe pile（PCC pile） is mainly presented by the difference of velocity responses at the points with different radius angles between exciting and receiving points. Based on the analytical formula founded by the authors, the dynamic response characteristics of every vibration modes are studied. The variations of total velocity responses on pile top along circumferential and radial directions are analyzed. The research indicates that： the total velocity response at 90 point mainly derives from the axisymmetric mode. The reflected wave crests at 45°, 135° and 180° point are close to the axisymmetric mode; but the incident wave crests have a greater difference. The total responses on pile top mainly derive from the first order vibration mode along radial direction, while the other modes along radial direction have little contribution. The velocity responses are the superposition of low order modes; but the circumferential modes higher than tenth order have little contribution. The incident wave crests derive from many modes, while the reflected wave crests mainly derive from the axisymmetric mode. The high-frequency interference waves mainly derive from the first order non-axisymmetric mode, the peak value and phase of which are different from various points. The high-frequency interference at 90° point is the least; and the phase from 0° to 90° point is contrary to that from 90° to 180° point. The velocity responses have little difference among different points along radial direction but have great difference along circumferential direction.

关 键 词：大直径管桩 低应变检测 三维效应 振动响应 解析解 

分 类 号：TU473[建筑科学—结构工程]